Re: panic: kmem_malloc(131072): kmem_map too small (AMD64)

Ruslan Ermilov wrote:
> On Sat, Sep 22, 2007 at 11:37:37PM +0200, Kris Kennaway wrote:
>> Darren Reed wrote:
>>> Kris Kennaway wrote:
>>>> Larry Rosenman wrote:
>>>>> On Fri, 21 Sep 2007, Kris Kennaway wrote:
>>>>>
>>>>>> Larry Rosenman wrote:
>>>>>>> I'm a heavy ZFS user, and got the following panic on 2007-09-18 
>>>>>>> source/world:
>>>>>> This is a FAQ, please see the archives (you need to increase the 
>>>>>> vm.kmem_size to provide more memory to ZFS).
>>>>> I thought that was only for i386, and it hadn't been an issue before.
>>>> Nope.  It is also load-dependent.
>>> So I just received this courtesy of ZFS:
>>> panic: kmem_malloc(131072): kmem_map too small: 343027712 total allocated
>>> cpuid = 0
>>> KDB: enter: panic
>>> This was with these settings in loader.conf:
>>> vm.kmem_size=419430400
>>> vm.kmem_size_max=419430400
> 
> Setting both doesn't make sense; kmem_size will take over.
> kmem_size_max only limits the automatically computed value
> of kmem_size, which is:
> 
> /*
>  * How many physical pages per KVA page allocated.
>  * min(max(max(VM_KMEM_SIZE, Physical memory/VM_KMEM_SIZE_SCALE),
>  *     VM_KMEM_SIZE_MIN), VM_KMEM_SIZE_MAX)
>  * is the total KVA space allocated for kmem_map.
>  */
> 
>>> vfs.zfs.arc_max=409715200
>>> (That's 400M, 400M and 40M, respectively.)
>>> Stupid question, perhaps, but is vm.kmem_size/vm.kmem_size_max limited by 
>>> physical RAM?
>> Yes.
>>
> To be precise, it's actually limited by 2 * sizeof(physical RAM).
> It's still size of a _virtual_ memory map (kmem_map), after all:
> 
> :	/*
> : 	 * Limit kmem virtual size to twice the physical memory.
> : 	 * This allows for kmem map sparseness, but limits the size
> : 	 * to something sane. Be careful to not overflow the 32bit
> : 	 * ints while doing the check.
> : 	 */
> : 	if (((vm_kmem_size / 2) / PAGE_SIZE) > cnt.v_page_count)
> : 		vm_kmem_size = 2 * cnt.v_page_count * PAGE_SIZE;

Well OK, but that seems pretty dangerous, because it leaves open a 
pathway to exhaust all of physical memory and presumably panic.

Kris